Resistance to treatment in depression is a huge problem: In 2007, a report from a huge study (STAR*D) stated that less than half of patients show a good clinical response to an initial antidepressant treatment, and approximately 30% do not show remission after four sufficient treatment trials (Warden et al., 2007). This is a pattern that is also reflected in other areas of mental health. While physical health is characterised based on biological abnormalities, mental health hasn't yet managed to use this approach. However, research shows that biological alterations do exist in many people with psychological diagnoses. We are examining characteristics - both neurobiological, social, cognitive, behavioural and emotional - that cluster with response to treatment, with the objective of delineating clinically distinct subpopulations within mood disorder sufferers, so that in the future more efficacious treatment that is personalised and may also prevent relapse.